She served three terms in the House of Delegates from 1997 to 2002 before being elected to the state Senate in 2003. In 2007, Mrs. Davis lost her seat to Sen. J. Chapman “Chap” Petersen, Fairfax Democrat, in the most expensive state Senate race in the commonwealth’s history with a price tag of about $3.5 million, according to the Virginia Public Access Project, a nonpartisan political money tracker in the state.

Ms. Davis said in email that she plans to leave her post in Gov. Bob McDonnell’s administration as director of the Virginia Liaison Office at the end of the month to “begin traveling around Virginia, full-time, to talk with Republicans throughout Virginia.”

In the mid-2000s, she was a political breed now practically extinct — a Northern Virginia Republican in the state Senate.

In 2007, she notably positioned herself to the left of much of her party on the issue of gun control, garnering a high-profile endorsement from New York City Mayor Michael R. Bloomberg. He had publicly feuded with Mr. McDonnell, then Virginia’s attorney general, after New York City officials sued 27 gun dealers, including six in Virginia, for selling guns to undercover agents through illegal “straw purchases.” Mr. Petersen, meanwhile, won the endorsements of the National Rifle Association and the pro-gun Virginia Citizens Defense League.

Ms. Davis does not plan to make a “formal” announcement until after the November elections, citing the need to focus on the presidential and congressional elections in the fall.

“Unfortunately, there are several others who have already started their campaigns for LG, which has put me in the position of having to get started earlier than I had originally anticipated,” she wrote.

Mr. Stewart, who is most associated with Prince William County’s 2007 crackdown on illegal immigration, had just more than $400,000 in his campaign accounts at the end of the latest reporting period on June 30. Mr. Lingamfelter had $3,600, but only registered his campaign committee on June 11. A report was not available for Mr. Martin, who only recently declared his candidacy.

Pete Snyder, who is heading up Virginia Victory, the Republicans’ coordinated campaign in 2012, is also weighing a bid.

Aneesh Chopra, formerly the chief technology officer for President Obama, is the only Democrat to have declared his plans to run for lieutenant governor.

The position historically has been used as a launching pad — often an effective one — to run for governor, with Lt. Gov. Bill Bolling the most recent example.

Democrat Tim Kaine, now a U.S. Senate candidate, served as lieutenant governor before winning the top state job in 2005. Former Lt. Gov. John Hager lost his bid for the Republican gubernatorial nomination in 2001, while Democratic Lt. Gov. Don Beyer won the nomination but lost his gubernatorial race in 1997. L. Douglas Wilder served as Virginia’s lieutenant governor before he became the nation’s first elected black governor in 1990, while former Lt. Gov. Charles Robb, a Democrat, won the governorship in 1981 and later served two terms in the U.S. Senate.